Many hydrocarbon fuels have been used, each with their own advantages and drawbacks. Examples of such fuels include gasoline, natural gas, diesel, kerosene, jet fuel, LPG, heavy distillates, bunker fuel, ethanol, coal, other solid hydrocarbon fuels and the like. Chemical compounds have been used as fuel additives over the past century to improve various parameters, such as octane number, of various fuels. The use, and subsequent banning, of lead in gasoline has been known for a long time. Tetraethyl lead showed a positive effect on octane and a profoundly negative effect on the environment.
In addition to tetraethyl lead, several elements are known to have combustion catalyst characteristics in gasoline or other hydrocarbon fuels. Examples, in addition to lead, are manganese, iron, copper, cerium, calcium and barium. Each of these elements has advantages and disadvantages in particular applications. Drawbacks of certain iron compounds include limited solubility in gasoline, toxicity, and expense as an additive. Interaction with sulfur and creation of sulfide precipitate may also occur, which is undesirable.
Another commonly-used additive in gasoline is MTBE. While this compound boosts octane levels significantly, the compound is thought to be carcinogenic. Also, it mixes easily with water which is hazardous should there be a leak. Gasoline containing MTBE leaking from an underground tank at a gas station could potentially leach into groundwater and contaminate wells. As a result of the believed negative potential of MTBE on the environment, ethanol is also being evaluated as a gasoline additive to boost octane.
In addition to the industry goal of improved combustion efficiency, smoke emissions reduction is also a concern, particularly for diesel fuel applications. The industry has not made substantial progress on development of a fuel additive for reducing smoke and particulate emissions
Finally, adjustment of combustion parameters is made to attempt to maximize function to reduce CO and NOx. In spite of these and combinations of these attempts to minimize pollutants, fuel combustion continues to be a focus of interest to improve fuel efficiency and reduce pollutants.
A fuel additive that includes a combustion catalyst to reduce smoke and particulate emissions from bus, truck and automobile engines operating on gasoline fuels would be advantageous. Also advantageous would be a fuel additive that increases efficiency and/or decreases pollutants for diesel fuel applications. It would be advantageous to reduce smoke, particulate and nitrogen emissions from fuel applications. An additive that does not result in the formation of precipitates would be also advantageous. An additive for hydrocarbon fuel that reduces level of NOx produced would also be advantageous. Finally, an additive that remains stable during the combustion process would be advantageous.